For many years portable electronic communication devices have become more multi-functional. Particularly mobile phones but also some others such as laptop and palmtop computers have expanded their original voice communication function to include Internet access, Bluetooth coupling, GPS (global positioning system), FM radio, RFID (radio frequency identification) sensing, secure data storage, and the like. Many commonly available mobile terminals are also multi-radio devices, which have disparate cellular radios and antennas so users can readily find an operating network in any of numerous countries they may travel. Each of these radios, whether cellular, Bluetooth, WLAN (wireless local area network) or the like, require an antenna particularly adapted for the requisite frequency band.
Another obvious trend in mobile communication devices is size; users want mobile phones that have greater capabilities but in a smaller overall package. This causes difficulty in arranging the physical placement of antennas for the various radios within the terminal housing, since that crowded electrical environment leaves few locations for antenna placement. Often a single antenna radiator element may be tuned to cover two or more radio frequency bands, but multiple antennas are still the norm for most mobile terminals given that most include several of the disparate radios listed above. Antenna placement is critical to alleviate parasitic coupling and to assure a reasonable gain at the desired bandwidth, and to meet other performance metrics such as standing wave ratio SWR.
Particularly antennas for Bluetooth frequencies have been disposed in the physical area of the mobile terminal keypad. See for example International Patent Publication No. WO 2008/059315 entitled “Positioning Conductive Component Adjacent an Antenna” by Nokia Corp. (published 22 May 2008), in which a key dome, adjacent within about 10 mm to an antenna, is decoupled by an inductor at operational frequencies of the antenna. But the keypad area is quite crowded electrically and even this 10 mm spacing becomes restrictive to the circuit designer seeking to integrate antennas into the overall mobile terminal. What is needed in the art is a more adaptable antenna solution that does not so restrict the circuit designer's options, at least for one antenna operating in one band and optimally for antennas operating across multiple bands.
Other related teachings include the following references:                US 2009/0251384, in which radio-frequency transceivers transmit and receive signals using key antennas;        WO 09/01158, in which the electrical length of the ground plane changes depending on an interconnecting mechanism configuration;        U.S. Pat. No. 7,383,067, in which a pattern of conductive traces forming an antenna circuit is positioned in a lower housing portion with keyboard circuitry;        